(1) Field of the Invention
This invention relates to a contact structure; and, in particular, to a contact terminal for use as an edge connector for a printed circuit board.
(2) Disclosure Statement
There are known various snap-in contact structures for use as an edge connector to a printed circuit board or other conductor equipped panels. Such a connector is ordinarily an elongated structure with a body part formed of an insulating material having a longitudinally extending slot or channel along one side to receive an edge portion of a printed circuit board. The insulating body part also receives a plurality of conductive terminals for making contact with conductive strips on the printed circuit board. The terminals are disposed in longitudinally spaced relation along the slot and isolated electrically from each other.
When a conductor equipped panel is inserted into the connector, the contact terminals engage and thereby make electric connections with the conductors of the panel. Each of the contact structures is connected individually to one of a plurality of lead wires. Such connection can be made before the terminals are mounted within the insulating body part. A common arrangement for establishing an interconnection between the terminals and connector body requires the terminals to be compressed or otherwise momentarily distorted during insertion thereof into the connector body. It has been found that such distortion (beyond the residual distortion after complete connection) of the contacts, although momentary, can be sufficient to give the contact a permanent set which tends to destroy the essential resilience thereof that assures the frictional grip of the contact with the aligned conductor of a panel inserted into the connector.
It is also recognized that providing an appropriate contact pressure or spring tension for the terminal can be difficult. A high contact pressure is desirable to maintain a good electrical connection between the terminal and the conductive strip on the printed circuit board. However, a relatively high contact force has a tendency to damage the conductive strips on a printed circuit board thereby causing a circuit discontinuity or limiting the number of circuit board insertions and removals without damage.
On the other hand, a relatively low terminal mating or engagement force is desirable to facilitate easy insertion of the printed circuit board into the connector. That is, a large number of terminals in the connector can make insertion of the printed circuit board into the connector a difficult task. If the connector has but one spring contact, the resistive force exerted thereby on a printed circuit board inserted into the connector is not sufficiently large that it creates a problem. However, if the connector has a plurality of contacts oriented in a row so that each such contact resists insertion of a single printed circuit board into the connector, the cumulative forces make initial insertion of the printed circuit board quite difficult. This is the situation with an edge connector for a printed circuit board which is equipped with a plurality of conductors each adapted to be connected to one spring contact. Further, during assembly of the contact structure, it is desirable that the conductive terminals can be easily and quickly inserted into the connector and secured in a fully inserted position.
Many known terminals for use with printed circuit boards are undesirably large for use in current automotive applications, where smaller and lighter components are being sought. Placing such terminals side by side produces an undesirably large printed circuit board and requires a larger connector. An attempt at simple down-sizing of the terminal may produce a terminal with insufficient contact pressure and attendant electrical discontinuity, unreliability and customer dissatisfaction.
Among the known terminals are those which have a contact spring pivoting at the forward end of the terminal. Thus, the electrical contact point between the contact spring and the conducting strip is rearward of the spring pivot point at the forward part of the terminal. Such rearward positioning of the contact point requires a longer printed circuit board ledge than would be required if the contact point were positioned closer to the forward portion of the terminal. As can be appreciated, a longer printed circuit board edge increases the weight and size of the circuit board assembly. These are some of the problems this invention overcomes.